JP7067426B2 - Electrode manufacturing method - Google Patents

Description

The present invention relates to a method for producing a band-shaped electrode by forming an electrode mixture layer on the surface of a current collector foil.

Conventionally, there has been known a technique for manufacturing a long electrode by forming an electrode mixture layer on the surface of a long current collector foil while transporting the current collector foil. For example, Patent Document 1 describes a manufacturing apparatus for forming an electrode mixture layer on both sides of a current collector foil, leaving both ends in the width direction, and pressing the formed electrode mixture layer to manufacture an electrode. It has been disclosed. In Patent Document 1, a stepped roll having a diameter larger than the range facing the electrode mixture layer at both ends is pressed against the electrode to form a large diameter portion provided at both ends of the stepped roll in the axial direction. Disclosed is a technique of pressing both ends in the width direction of the electrode to stretch the current collecting foil in the portion where the electrode mixture layer is not formed.

Japanese Unexamined Patent Publication No. 2018-106813

However, when a stepped roll having a large diameter at both ends is pressed while transporting a long electrode, the electrode may bend toward the center in the width direction. When the electrode is bent, the position where the stepped roll is pressed is not stable, and it may not be possible to properly stretch the entire current collector foil in the portion where the electrode mixture layer is not formed.

The present invention has been made to solve the problems of the above-mentioned conventional techniques. That is, the object thereof is to provide a technique for suppressing the bending of the electrode in the width direction at the time of pressing by the stepped roll.

The method for manufacturing an electrode according to one aspect of the present invention, which has been made for the purpose of solving this problem, is a coating method in which an electrode mixture layer is formed on the surface of the collector foil in the width direction of a long collector foil. A method for manufacturing an electrode for manufacturing an electrode having a portion and an uncoated portion on which the electrode mixture layer is not formed, wherein the electrode is conveyed in the longitudinal direction and faces the uncoated portion. Between a stretch roll having a diameter larger than the diameter of the portion facing the coated portion and a guide roll having a uniform diameter as a whole in the axial direction and provided facing the stretch roll. A stretching step of passing the electrode and a pressing step of pressing the electrode mixture layer of the electrode in the thickness direction are included. In the stretching step, the holding angle of the electrode to the guide roll is 45 ° to 180 °. Within the range, the guide roll is pressed toward the stretched roll.

According to the method for manufacturing an electrode in one aspect described above, in the stretching step, the electrode is wound around a guide roll facing the stretching roll, which is a stepped roll, with a holding angle in the range of 45 ° to 180 °, and the guide roll is stretched. Press on. When the guide roll around which the electrode is wound is pressed against the stretching roll, an outward tension in the width direction is applied to the electrode. That is, the electrodes are conveyed in a shape along the outer circumference of the guide roll. Therefore, the position of the electrode during transportation is stable, and the possibility that the electrode bends toward the center in the width direction is small.

According to the present invention, a technique for suppressing bending in the width direction of an electrode when pressed by a stepped roll is realized.

It is explanatory drawing which shows the electrode of this embodiment. It is a schematic block diagram of a part of a manufacturing apparatus. It is explanatory drawing which shows the stretched part. It is explanatory drawing which shows the stretched part. It is explanatory drawing which shows the stretched part. It is explanatory drawing which shows the bending amount. It is explanatory drawing which shows the experimental result.

Hereinafter, the embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a manufacturing method for manufacturing a long electrode.

The electrode 10 manufactured by the manufacturing method of the present embodiment has a current collector foil 11 and an electrode mixture layer 12 as shown in FIG. 1 in a cross section thereof. The current collector foil 11 is a long metal foil having a width W. The electrode mixture layer 12 is a layer made of a material containing an electrode active material, and is formed on both sides of the current collector foil 11.

The electrode mixture layer 12 is partially formed in the width direction of the current collector foil 11, and the current collector foil 11 is exposed in the rest. Specifically, the electrode mixture layer 12 is formed in the range of the width W1 (<W) of the central portion in the width direction of the current collector foil 11, and is formed in the range of the width W2 (<W1) at both ends. Is not formed. In the following, among the electrodes 10, the range where the electrode mixture layer 12 is formed is referred to as a coated portion 13, and the range where the electrode mixture layer 12 is not formed is referred to as an uncoated portion 14. That is, the uncoated portion 14 is a portion of the electrode 10 where the current collector foil 11 is exposed. The uncoated portion 14 is smaller in thickness than the coated portion 13.

The electrode 10 of this embodiment is used, for example, in a lithium ion secondary battery. The electrode 10 manufactured by the manufacturing method of this embodiment may be, for example, an electrode 10 for a positive electrode in which an electrode mixture layer 12 containing a positive electrode active material is formed on a current collector foil 11 made of aluminum, or a copper current collector. The electrode 10 for the negative electrode may be used in which the electrode mixture layer 12 containing the negative electrode active material is formed on the foil 11.

An example of a method for manufacturing the electrode 10 will be described. In the manufacturing method of this embodiment, a long current collector foil 11 is conveyed in the longitudinal direction, and a layer of a mixture of an electrode mixture and a solvent is formed on the surface thereof. The layer of the mixture is applied to the current collector foil 11 as a paste in which each material of the electrode mixture is dispersed in a solvent, for example. Alternatively, the layer of the mixture is pressure-bonded to the current collector foil 11 in the form of agitated granules of, for example, a small amount of solvent and each material of the electrode mixture. Further, the electrode 10 is dried in a drying oven or the like, the solvent in the layer of the mixture is removed, and then the electrode 10 is once wound into a roll. As a result, the electrode 10 has the electrode mixture layer 12 formed on the current collector foil 11.

Next, as shown in FIG. 2, the electrode 10 is unwound from the roll 21, pressed by the pressing device 22, and then wound on another roll 23. The press device 22 is a device including a press roll pair 221. In the pressing process by the press device 22, the electrodes 10 are pressed in the thickness direction by pressing the press roll pairs 221 in a direction close to each other while passing the electrodes 10 between the press roll pairs 221. By pressing with the pressing device 22, the electrode mixture layer 12 is compressed to become a layer having a predetermined thickness and a basis weight (density).

The press roll pair 221 is a pair of rolls having a uniform diameter in the axial direction. On the other hand, as shown in FIG. 1, since the electrode 10 has a different thickness between the coated portion 13 and the uncoated portion 14, the press pressure is applied to the thick coated portion 13. Therefore, it hardly participates in the unpainted portion 14 having a small thickness. Since the current collector foil 11 of the coated portion 13 also stretches to some extent by pressing, the amount of stretch of the current collector foil 11 differs between the uncoated portion 14 and the coated portion 13 simply by pressing. .. This difference in the amount of elongation can cause wrinkles and warpage of the current collector foil 11 when it is wound around the roll 23.

The manufacturing method of this embodiment includes a stretching step before the pressing step by the pressing device 22. As shown in FIG. 2, the stretching step is a step of stretching the current collector foil 11 of the uncoated portion 14 by the stretching portion 30 arranged in the front stage of the press device 22.

As shown in FIGS. 3 and 4, the stretched portion 30 includes a stretched roll 31 and a guide roll 32. FIG. 4 is a view of the stretched portion 30 viewed from the lower right to the upper left of the stretched portion 30 in FIG. 3, as shown by an arrow A in FIG. In FIG. 3, all the rolls other than the stretching portion 30 and the pressing device 22 are omitted.

As shown in FIGS. 3 and 4, the stretch roll 31 is a stepped roll and is arranged in a direction orthogonal to the transport direction of the electrode 10. The small diameter portion 311 at the central portion in the axial direction of the stretch roll 31 is formed to have a smaller diameter than the large diameter portions 312 at both ends. The small diameter portion 311 has a width similar to the width W1 of the coated portion 13 of the electrode 10, and the large diameter portions 312 on both sides have a width equal to or larger than the width W2 of the uncoated portion 14 of the electrode 10. The large-diameter portions 312 on both sides have the same diameter, and are arranged so as to face the uncoated portion 14 of the electrode 10. Further, the difference in diameter between the large diameter portion 312 and the small diameter portion 311 is larger than the thickness of the electrode mixture layer 12 before pressing.

The guide roll 32 is a roll made of resin having a uniform diameter as a whole, and is a roll having a length equal to or larger than the width W of the electrode 10 in the axial direction. The guide roll 32 is, for example, a roll having a diameter equivalent to that of the large diameter portion 312 of the stretched roll 31 and longer than the length of the stretched roll 31. The guide roll 32 is arranged in parallel with the stretching roll 31 at a position on the upstream side of the stretching roll 31 in the transport direction of the electrode 10 and facing the stretching roll 31.

At the time of manufacturing the electrode 10, the stretch roll 31 is rotationally driven at a predetermined speed according to the transport speed of the electrode 10. The guide roll 32 is a driven roll that is not rotationally driven, and as shown in FIG. 5, the guide roll 32 is pressed against the stretching roll 31 with a pressing force F with the electrode 10 interposed therebetween. The electrode 10 is wound around the guide roll 32 at a holding angle θ while being conveyed from the lower left to the upper right in FIG. Further, the electrode 10 passes through a portion where the guide roll 32 and the stretching roll 31 face each other, is wound around the stretching roll 31, and is conveyed to the rear stage on the right side of the drawing.

In the manufacturing method of the present embodiment, the holding angle θ of the stretched portion 30 is set within the range of 45 ° to 180 °, and the guide roll 32 is pressed against the stretching roll 31 with a predetermined pressing force F. The pressing force F is, for example, 20N. By being wound around the guide roll 32 at a holding angle θ of 45 ° or more, the electrode 10 is subjected to outward tension in the width direction by the guide roll 32. That is, the electrode 10 has a shape along the outer circumference of the guide roll 32, and the electrode 10 is prevented from bending toward the center. Therefore, since the large diameter portion 312 of the stretch roll 31 is pressed against the entire area up to the boundary between the uncoated portion 14 and the coated portion 13 of the electrode 10, the entire uncoated portion 14 of the electrode 10 is appropriately pressed. It is stretched. After that, by being pressed by the pressing device 22, the amount of elongation of the current collecting foil 11 of the electrode 10 becomes about the same in the coated portion 13 and the uncoated portion 14.

Next, the results of an experiment for examining an appropriate range of the holding angle θ of the guide roll 32 of the present embodiment will be described. In this experiment, the pressing force F (see FIG. 5) was set to 0N or 20N, and the holding angles θ were changed to 0 °, 45 °, 90 °, and 180 ° to manufacture the electrode 10. Then, the transport position of the electrode 10 immediately after the stretched portion 30 in the manufacturing process and the bending amount R of the electrode 10 after passing through the press device 22 were measured. In each Example and Comparative Example, only one of the holding angle θ and the pressing force F was changed, and the other conditions were the same.

In this experiment, the position where the end portion in the width direction of the electrode 10 passed was detected by the edge sensor 33 shown in FIG. 4, and the deviation width of the transport position of the electrode 10 from the ideal position was calculated. Further, a sensor similar to the edge sensor 33 was arranged at a position downstream of the press device 22 in the transport direction of the electrode 10, the passing position of the end portion of the electrode 10 was detected, and the bending amount R was calculated. In this experiment, for example, as shown in FIG. 6, the maximum value of the difference in the position of the end portion in the width direction of the electrode 10 for 2 m in the longitudinal direction was defined as the bending amount R. The standard of the bending amount R is 3 mm or less.

The results of this experiment are shown in FIG. Examples 1 to 3 are examples in which the guide roll 32 is pressed toward the stretched roll 31 with the holding angle θ of the stretched portion 30 within the range of this embodiment. Specifically, in Examples 1 to 3, the pressing force F was set to 20 N, and the holding angle θ was set to 45 ° in Example 1, 90 ° in Example 2, and 180 ° in Example 3, respectively. As shown in FIGS. 7, in Examples 1 to 3, the transport position has a deviation from the ideal position in the range of ± 0.5 to 0.7 mm, and the bending amount R has a maximum of 0 ± 1. It was within a good range of 0 mm.

On the other hand, Comparative Examples 1 to 5 are examples in which the holding angle θ or the pressing force F of the stretched portion 30 is out of the range of this embodiment. Specifically, in Comparative Examples 1 to 4, the pressing force F was set to 0N, and the holding angles θ were set to 0 °, 45 °, 90 °, and 180 °. That is, the guide rolls 32 of Comparative Examples 1 to 4 are not pressed toward the stretched roll 31, but are merely in contact with each other via the electrode 10.

Further, Comparative Example 5 is an example in which the holding angle θ is set to 0 ° and the pressing force F of 20N is used for pressing. That is, in Comparative Example 5, the electrode 10 is conveyed toward the stretching roll 31 without being wound around the guide roll 32. The guide roll 32 is simply pressed against the stretching roll 31 from a position symmetrical with the stretching roll 31 across the transport path of the electrode 10.

As shown in FIG. 7, in all of Comparative Examples 1 to 5, there was a place where the transport position deviated by ± 1.0 mm or more from the ideal position. It is considered that the cause of this deviation includes the deflection of the electrode 10 in the width direction. Further, the bending amount R of Comparative Examples 1 to 5 was 0 ± 3.0 mm or more, which was not good.

As shown in the results of this experiment, the guide roll 32 is pressed toward the stretching roll 31 with the holding angle θ in the range of 45 ° to 180 ° (in this experiment, the pressing force F is 20N). It was confirmed that the transport position of the electrode 10 could be stabilized and the bending amount R at the end of the electrode 10 could be within the standard range.

As described in detail above, the method for manufacturing the electrode of the present embodiment includes a stretching step by a stretching portion 30 including a stretching roll 31 which is a stepped roll and a guide roll 32 arranged to face the stretching roll 31, and a press. It includes a pressing process by the apparatus 22. Then, in the stretching step, the holding angle θ of the electrode 10 to the guide roll 32 is set within the range of 45 ° to 180 °, and the guide roll 32 is pressed against the stretching roll 31. As a result, the bending of the electrode 10 in the width direction in the stretching step is suppressed, so that the entire uncoated portion 14 can be stretched, and the electrode 10 having less curvature can be manufactured.

It should be noted that this embodiment is merely an example and does not limit the present invention in any way. Therefore, as a matter of course, the present invention can be improved and modified in various ways within the range not deviating from the gist thereof. For example, the present invention is not limited to the electrode 10 in which the electrode mixture layer 12 is formed on both sides of the current collector foil 11, but the present invention is a method for manufacturing an electrode in which the electrode mixture layer 12 is formed only on one side of the current collector foil 11. It is also applicable to.

Further, the present invention is not limited to the electrode 10 in which the uncoated portion 14 is provided only on both ends in the width direction, and the electrode is not limited to the electrode 10 in which the coated portion is formed in a striped shape. It can also be applied to a method of manufacturing an electrode having an uncoated portion. In that case, it is preferable to use a stretch roll having a large diameter portion facing all the uncoated portions.

Further, in the present embodiment, the stretched roll 31 having the large diameter portion 312 and the small diameter portion 311 is used, but a roll in which only the large diameter portion 312 is formed on the rotating shaft may be used. Further, the diameter of the guide roll 32 is not limited to the same as that of the large diameter portion 312 of the stretch roll 31, and may be any size. Further, the guide roll 32 is not limited to the resin roll, and may be, for example, a metal roll.

Further, in the present embodiment, the stretching step is performed before the pressing step, but the stretching step may be performed after the pressing step. Alternatively, the stretching step may be performed both before and after the pressing step.

Further, in the present embodiment, the guide roll 32 is arranged on the upstream side of the stretching roll 31 in the transport direction of the electrode 10, but it may be on the downstream side. Alternatively, the guide rolls 32 may be arranged on both the upstream side and the downstream side.

10 Electrode 11 Current collector foil 12 Electrode mixture layer 13 Coated part 14 Uncoated part 31 Stretching roll 32 Guide roll 221 Press roll pair

Claims (1)

In the width direction of the long current collector foil, an electrode having a coated portion in which an electrode mixture layer is formed on the surface of the current collector foil and an uncoated portion in which the electrode mixture layer is not formed is provided. It is a manufacturing method of the electrode to be manufactured.
A stretch roll having the electrode conveyed in the longitudinal direction and having a diameter of a portion facing the uncoated portion larger than the diameter of the portion facing the coated portion, and a roll having a uniform diameter as a whole in the axial direction. The stretching step of passing between the guide roll provided facing the stretching roll and the stretching step.
A pressing step of pressing the electrode mixture layer of the electrode in the thickness direction, and
Including
In the stretching step, the guide roll is pressed toward the stretch roll with the holding angle of the electrode to the guide roll within the range of 45 ° to 180 °.
A method for manufacturing an electrode.

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